The increasing miniaturization of computer digital circuitry and other components has enabled a corresponding increase in computer power and decrease in the cost of creating powerful computing devices. However, certain critical components have not progressed as rapidly with respect to miniaturization, and the effects of this lag are beginning to limit the overall miniaturization of computing devices. For example, electronic switches (as opposed to purely solid state electrical switches such as transistors) are inherently mechanical in nature, and as such rely on forming and shaping steps that are not critical with respect to purely electrical systems.
Before discussing microelectromechanical switch technology, a brief discussion of solid state switch technologies will be presented. Typically, a solid-state switch comprises a transistor element such as a FET (Field Effect Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), JFET (Junction Field Effect Transistor), MESFET (Metal Semiconductor Field Effect Transistor), etc. Typically, transistor devices will operate in an essentially linear manner over only a small gate voltage region, outside of which the device is either off or saturated. The off and saturated states are useful for switching applications.
There are a number of difficulties associated with the production and use of solid-state switches such as those discussed above. Drawbacks include high insertion losses, high contact resistance, high switching capacitance, signal and gate cross-coupling, high-frequency electronic noise, reliance on semiconductor properties (with attendant requirements for heavy fabrication process control), and out diffusion difficulties. For these reasons, microelectromechanical devices may be more suitable in certain miniature switch applications.
An example of such a switch is the microelectromechanical switch described in U.S. Published Application 2003/0122640 to Deligianni et al. The device described in that application comprises a movable part, two pairs of contacts, and actuators. The movable part is laterally or pivotally deflected by the actuators to make or break connections across pairs of contacts. While the device is said to solve certain shortcomings inherent in the production and use of solid state switches and some microelectromechanical switches, many problems remain. For example, precise fabrication control with respect to pivots, brackets, etc. is required to ensure that the actuator is movable within the required bounds but that it does not stray a prohibitive amount from its intended range and path of travel. Moreover, the quality of the ohmic contact produced depends upon the precision with which the actuator moves, and hence the precision with which the various mating parts are fabricated. Moreover, the actuator experiences flexion stresses, which, while perhaps less severe than experienced in prior designs, may still cause fatigue with long-term usage.
For these reasons and others, a microelectromechanical switch is needed that eliminates the drawbacks of former solid state switches and microelectromechanical switches alike.